Deep in the bowels of an icy mountain on an island above the Arctic Circle between Norway and the North Pole lies a resource of vital importance for the future of human­kind. It’s not coal, oil or precious minerals, but seeds. Millions of these tiny brown specks, from more than 930,000 varieties of food crops, are stored in the Global Seed Vault. It is essentially a huge safety deposit box, holding the world’s largest collection of agricultural biodiversity.

The vault, can be a way of preserving historical species of plants and protect these seeds for future generations. The seeds in the Seed Vault are duplicate copies of collections held in national and other seedbanks around the world. If something happens to one of those facilities and if their seed samples are destroyed, then there is a backup copy in the Seed Vault. In the past the loss of a variety meant extinction for that variety and any unique trait it might have contained. Today, fires, floods, natural disaster, war, human error, accidents, funding cuts — none of these needs cause the extinction of a crop variety. If that variety is in the Seed Vault, it’s as safe as it can be.

Though the vault is thought of as a “doomsday vault”, that will be the source of seeds for the world after a worldwide disaster, that isn’t true. The seeds are not meant for distribution to farmers or gardeners. Their value and utility lie in their being a genetic resource in plant breeding. So, they are ultimately intended to serve plant breeders and other scientists who are involved in developing new crop varieties for farmers. Think of the seeds as a collection of traits, or even more broadly as a collection of options our crops will have in the future, options such as disease and pest resistance, drought and heat tolerance, better nutrition, etc.”

In order, to preserve these seeds at 0 F, the seeds are sealed in three-ply foil packages and then sealed inside boxes. These boxes are placed on shelves inside the vault where temperature and moisture levels are closely monitored. This process helps keep the metabolic activity in the seeds low, keeping them viable for long periods of time.

The Global Seed Vault can hold massive amounts of seeds. It is built to store a whopping 4.5 million varieties of crops, with each variety containing around 500 seeds. That equals a maximum of 2.5 billion seeds that can be stored in the Vault. The vault currently holds more than 860,000 seed samples. These seeds were donated by almost every country in the world, so there is a massive variety of seeds represented in the Global Seed Vault.

Does hot water freeze faster than cold water? It seems obvious that the answer should be no, because hot water takes longer to cool down, and so it couldn’t possible freeze faster. But hot water seems to freeze faster than cold water, this effect is known as the Mpemba effect. The effect was named after the Tanzanian student who in 1963 noticed that hot ice cream mix freezes faster than a cold one.

Now a team of physicists from the Nanyang Technological University in Singapore, led by Xi Zhang, have found evidence that it is due to the unique properties of the different bonds that hold water together that provide this effect.

Let’s get to know what’s so odd about the bonds in water? Each water molecule consists of a relatively large oxygen atom joined to two smaller hydrogen atoms by standard covalent bonds. But when you put water molecules together, the separate water molecules are also bound together by weaker forces generated by hydrogen bonds. These forces occur when a hydrogen atom from one molecule of water sits close to an oxygen atom from another.

The team suggests that these are the bonds that cause the Mpemba effect. They propose that when the water molecules are brought into close contact, a natural repulsion between the molecules causes the covalent bonds O-H bonds to stretch and store energy. But as the liquid warms up, it forces the hydrogen bonds to stretch and the water molecules sit further apart. The stretching in the hydrogen bonds allows the covalent bonds to relax and shrink somewhat, which causes them to give up their energy. The process of covalent bonds giving up their energy is essentially the same as cooling, and so warm water should in theory cool faster than cold. And that’s exactly what is observed in the Mpemba effect. The team’s calculations suggest that the magnitude of the covalent bond relaxation accounts for the experimental differences in the time it takes for hot and cold water to freeze.

So while these guys may well have solved the riddle of Mpemba effect, they will probably need to work a little harder to convince everyone. Nevertheless, interesting stuff!

]]>http://uncanny.in/2018/01/22/does-hot-water-freeze-faster-than-cold-water/feed/0How 1KG defined Worldwidehttp://uncanny.in/2018/01/19/how-1kg-defined-worldwide/
http://uncanny.in/2018/01/19/how-1kg-defined-worldwide/#respondFri, 19 Jan 2018 18:42:05 +0000http://uncanny.in/?p=4Have you ever imagined what does a kilogram weigh? In middle school science classes we have often been taught that the unit is based on the weight of water—specifically a cube of water, a tenth of a meter on each side, at just above freezing. This used to be the case, but it isn’t actually true anymore—since 1875, the kilogram has been defined by one specific platinum cylinder, known affectionately as “Le Grande K” and officially as “the International Prototype Kilogram,” or IPK. It stands an inch-and-a-half high and wide and is housed in a vault outside Paris, inside three concentric glass containers to protect it from dust and other weight-altering debris.

Every scale in the world is ultimately based on the IPK, which was commissioned by the General Conference on Weights and Measures. But the IPK’s uniqueness may be its downfall. Even handling the model kilogram with your fingers will leave oil, changing its weight ever so slightly therefore it is rarely removed from its enclosure, and never transported to other areas.

That’s why for decades, metrologists have strived to retire ‘Le Grande K’ — the platinum and iridium cylinder that for 126 years has defined the kilogram from a high-security vault outside Paris. The breakthrough comes in time for the kilo­gram to be included in a broader redefinition of units — including the ampere, mole and kelvin.It is expected that the definition of the kilogram and several other units will change on May 20, 2019, following a final vote by the General Conference on Weights and Measures in November 2018.Now it looks as if they at last have the data needed to replace the cylinder with a definition based on mathematical constants.The new definition will use only invariant quantities of nature: the Planck constant, the speed of light in vacuum, and the caesium hyperfine frequency.